River, southern Quebec, Canada. It is 325 mi (523 km) long and a major tributary of the Saint Lawrence River, flowing south from Gouin Reservoir into the St. Lawrence at Trois Rivières. It is a major logging river, serving large pulp and paper factories at La Tuque, Grand-Mère, Shawinigan, and Trois Rivières. Since 1900 it has also been a major source of hydroelectric power